Lubricating and cooling compound for cold reducing mills



Patented Dec. 16, 1947 LUBRICATING AND COOLING COMPOUND, FOR COLDREDUCING MILLS Harold F. Miller, Pittsburgh, and Samuel J. Moore,Munhall, Pa.

No Drawing. Application December '1, 1945,

Serial No. 633,522

6 Claims. (Cl. 252-492.)

A further object is the provision of lubricating and cooling compoundswhich stand up under more severe loads than prior art compositions;

thereby preventing metal to metal contact during cold rolling operationsand consequently minimizing roll wear.

A still further object is the provision of lubricating and coolingcompounds which do not carbonize during use and which prevent adherenceof oils or dirt to the metal being rolled, thereby facilitatingsubsequent cleaning of the same.

These and further objects of the invention will be apparent in thefollowing description.

In the formation of metal of thinner gauges, such as thin plates,strips, and sheets, it is now customary to carry out the latter part ofthe reduction of the metal from the ingot in cold rolling mills. Thus,reduction in gauge of strips and sheets in modern practice fromthicknesses approximating .09 inch is usually effected in continuouscold mills, which require the application of very high screw-downpressures in order to effect the desired reduction of the cold metal.

Because of the extremely high unit pressures existing between the stripand the rolls in the cold rolling mill, there is developed a largeamount of heat in the pass. This heat is absorbed both by the rolls andby the strip passing between them. Unless the heat is dissipated, itmay, after a period of operation, affect the strength of the rolls byoverheating them and heat the strip to a point where a temperature oftemper colors is reached or even surpassed. Thus, it is customary toemploy in the cold rolling of strip a cooling liquid which is sprayed onthe rolls and the strip to carry away much of the heat so developed.

Since metal to metal contact between the rolls and the strip isundesirable, due to a large amount of wear to the rolls which this wouldentaiL-it has been customary to use as a cooling compound one which alsohas lubricating properties, such that it will stand up under the highunit pressures between the rolls and the'strip, thus preventing metal tometal contact between rolls and strip. Because of their dual function,lubricating and cooling compounds used in the past have beencompromises; that is, they could -not be compounds which possessed thehighest heat capacity such as water, which is ideal for coolingpurposes, because such compounds are not good lubricants. 0n the otherhand they could not be oils alone, which would make the best lubricants,because of their low heat capacity. There have, therefore, been used inthe past as lubricating and cooling compounds for cold reducing millsmixtures or emulsions of water and lubricating oils which possess bothhigh heat capacity and good lubricating qualities.

In order to make such mixtures or emulsions of waterand oil as stable aspossible, emulsifying agents of various types, among them being sodiumor potassium hydroxide, have been employed. When used in a system ofwater and palm oil, sodium hydroxide, for instance, prevents thebreaking of the emulsion on standing in cooling tanks and inhibitscorrosion to a certain extent. In addition, sodium hydroxide facilitatesthe general handling of the resulting lubricating and cooling compound.Whereas judicious proportioning of oil, water, and emulsifying compound,such as sodium or potassium hydroxide, provides an adequate coolingmedium, the lubricating characteristics of the mixture do not reach thedesired high values.

It has been proposed, in order to improve the lubricating qualities ofsuch oil, water, and

I emulsifying compound mixture, to add to it small quantities of certaininorganic radicals, namely, phosphate and borate, such additions being,for example, in the form of phosphoric acid, monosodium phosphate,di-sodium phosphate, trisodium phosphate, or the correspondingphosphoric acid salts of potassium or ammonium. Whereas such additionsresult in an improvement in the stability of the emulsion and itslubricating qualities, the resulting compound still leaves something tobe desired as a lubricant, since it is prone to break down underextremely high unit pressures over extended periods of time.

We have found that the addition of an organic hydroxy-acid to the systemof water, lubricating oils of which palm oil is typical, and aninorganic salt yielding free base by hydrolysis and forming a solublesoap with the oil, produces a cooling and lubricating composition which,while retaining the desirable cooling characteristics of previous oiland water emulsions, possess outstandingly improved qualities as alubricant. Broadly our invention consists of a system composed of water,to which is added from 0.5 to 10% by weight of any saponifiable oil,preferably containing some free fatty acid, from 0.05 to 2% of aninorganic salt yielding free base by hydrolysis and forming a solublesoap with the oil, and from .05 to 2% of an organic hydroxy-acid havinga low dissociation constant and consequently a buffering reserve ofundissociated molecules.

In making the lubricating and cooling compound, the organic hydroxy-acidshould be added to the water after the oil and the emulsifying base, inorder to insure the optimum formation of the emulsion and the subsequentuniform coalescence of oil into particles of optimum size throughout thesystem by the action of the organic hydroxy-acid. Typical of the oilswhich may be used in the compound of the present invention are palm oilitself or palm oil in combination with stearic acid, palmitic acid, orother similar fatty acids. It is to be understood, however, that theinvention is not limited to the use of such specific oils, and that anyvegetable or animal oil preferably having some free fatty acid, may beused. The emulsifying inorganic salt preferably should be the salt of aweak di-basic or tri-basic acid, such as H3PO4 or H2003 and a solublesoap forming base such as KOH, NaOH, or NH-rOH. Typical of such salt ispotassium phosphate, although it is obvious that sodium phosphate,ammonium phosphate, and the correspondin carbonates may be used. It ispreferred to use potassium salt-s, however; because soaps of potassiumare liquid in addition to being soluble, whereas sodium soaps are hardand tend to gel at room temperatures, and ammonium soaps haveundesirable dissociation characteristics.

The acid employed is one or more of the organic hydroxy-acids,preferably citric, lactic, tartaric, malic, or gluconic acid. All theseacids have a low dissociation constant and consequently a bufferingreserve of undissociated molecules. It is desirable that the acidemployed have a binary or tertiary ionization. The acid content range ofthe composition, given above, is on the basis of solid commercialcitric, tartaric, malic, and gluconic acids and of 44% commercial lacticacid.

The improvement in lubricating value of compounds made in accordancewith our invention has been repeatedly demonstrated. In the testing oflubricants to determine whether or not they are suitable for varioususes, particularly 'those in which the service is severe, the Faville-LeVally (Falex) lubricant tester is of great value. Such tester wasemployed in this instance. The tester consists of a terminal bearing orspindle fixed to a shaft rotating at constant speed and suspended in thelubricant to be tested. On opposite sides of the terminal bearing andlikewise suspended in the lubricant are bearing blocks having V-shapedgrooves therein, so that the terminal bearing rotates in the grooves,The bearin blocks may be advanced toward each other by the jaws of aload applying mechanism, jaw load being regulated by means of a ratchetwheel turned by an eccentric feed arm. Measurement of the wear of theterminal bearing in the bearing blocks is made by countin the peripheralnotches through which the ratchet wheel is advanced. Jaw load isregistered in pounds, and torque applied to the terminal bearing ismeasured in pound-inches on separate gauges of the tester. In the tests,whose results are recorded in the following Tables I and II, the timewas recorded in decimal hours by a stop watch graduated in that manner.

New sets of terminal bearings and bearing blocks and 60 cubic centimeterquantities of each particular lubricant were employed in each test. Inorder to approximate as nearly as possible the conditions encountered inservice by a cold rolling mill lubricant, a final constant jaw load of2500 pounds was employed. After a .05 hour break-in period at 250 poundsjaw load, a period of increasing load (250 to 2500 lbs.) ofapproximately .03 hour duration was used in each test. In each of thetests recorded below, the actual test period at 2500 pounds jaw load hascontinued for .30 hour. The preliminary break-in period served thepurposes of eliminating surface irregularities on the terminal bearingand bearing blocks and in distributing the lubricant evenly over thebearing surfaces. The increasing load period was accomplished byengaging the feeder to apply the load automatically and continuously ata constant rate. The feeder was disengaged at the start of the constant2500 pound load test period, and was subsequently applied only when wearcaused the jaw load gauge reading to drop below 2500 pounds, The numbergiven in Table II for each sample, under each particular time,represents the total number of notches which the feed wheel of the Falextester was advanced up to that particular time in order to maintain the2500 pound load on the bearing blocks, and thus is a direct measure ofthe wear on the terminal bearing and the bearing blocks. The temperaturewhich the lubricant reached at the end of .30 hour was recorded in eachtest.

The following Tables I and II give the results of tests on the Falexdevice employing three lubricants, Nos. 1, 2 and 3, made up of water,palm oil, and potassium phosphate in the amounts indicated, threelubricants, made in accordance with the present invention, Nos/l, 5, and6, made up of water, palm oil, potassium phosphate, and solid commercialcitric acid, in the proportions given, and four lubricants, also made inaccordance with the present invention, Nos. 7, 8, 9, and 10, made up ofwater, palm oil, potassium phosphate, and 44% commercial lactic acid, inthe amounts indicated.

TABLE I [LUBRICANT COMPOSITION, PER CENT BY WEIGHT (REMAINDER 'ATERH YCitric Lactic Lubricant I\o. Palm 011 K31 O4 Acid Acid 1. 00 0. 10 1.0(1 0. 20 1. 00 O. "10 1. ()0 (1. 05 1.00 0. 1O 1. 00 0. 40 1. O0 0.10 1. 0C 0. 1O 1. 00 0. l0 2.00 0. 2A)

TABLE II Lubri Notches Wear under a 2500 lb. load Final Tom cantperature of No. .025 .05 .10 .15 .25 .30 l

hour hour hour hour hour hour hour 18 25 44 (i4 74 88 92 176 33 48 71 87116 144 176 54 77 110 146 173 201) 218 185 31 35 40. 45 48 5O 55 162 1114 18 24 29 31 33 15 20 25 26 28 30 30 167 18 20 23 25 26 27 29 llil 1115 15 15 25 25 27 170 17 19 21 26 28 29 31 15 18 20 22 24 25 31 181 Thebearing blocks employed in the tests on the Falex machine have bearingsurfaces in the form of a V and contact the terminal bearing, at leasttheoretically, along a line. Consequently, the load in pounds per squareinch imposed upon the terminal bearing and the bearing blocks is on theorder of thousands of times greater than the 2500 three lubricants notcontaining such organic hypound jaw load. Thus, the test duplicates orsurpasses the conditions which the lubricant meets in actual service, asfar as pressures are concerned, in the cold rolling of metals.Furthermore, the function of the lubricating and cooling compound in thetests is the same in other respects that it must perform on the coldreduction mill. That is, it must lubricate the bearing, offsetting thefriction normal to such high pressure loading, and at the same time itmust dissipate the heat produced by friction. The better the lubricant,the less is the wear, and the better the coolant, the lower is theoperating temperature. The test on the Falex machine is, in one respect,more severe than actual cold rolling operations. In the test, only 60cubic centimeters of lubricant is used, and consequently, it does nothave much opportunity to dissipate heat. In actual rolling millpractice, on the other hand, the lubricant is continuously circulatedback to a sump where it is cooled and cleaned prior to itsrecirculation.

The results of the ten tests recorded in the above tables strikinglyillustrate the improvement brought about by the addition to thelubricant of small amounts or organic hydroxy-acids, such as citric andlactic acids. The two important figures in Table II, in determining theworth of a lubricant for cold rolling purposes, are the total notcheswear at the end of the test, that is, at .30 hour, and the finaltemperature of the lubricant. As can be seen, with the use of lubricantsNos. 1, 2, and 3, although the final temperatures are not unduly high,reaching a maximum of 285 F. in the case of lubricant No. 3, the wear ineach instance is substantial, from 92 notches with lubricant No. 1 to218 notches with lubricant No. 3. Such large amounts of wear indicatethat, whereas these compositions may function satisfactorily ascoolants, they leave much to be desired as lubricants.

In all of lubricants Nos. 4 to 10, inclusive, including either citric orlactic acid, the coolant properties are satisfactory and in generalbetter than those of lubricants Nos. 1, 2, and 3, as evidenced by the,in general, lower final temperature of the lubricant, and thelubricating properties droxy-acids. Thus, the wear on the terminalbearing and bearing blocks with. lubricants Nos. 4 to 10, inclusive,ranges from a minimum 01 2'7 notches, in the case of lubricant No. 8, toa maximum of notches in the case of lubricant No. 4. Lubricant No. 4 isstill very much superior to lubricant No.1, which gave the minimum wear,92 notches, of the three prior art lubricants tested.- In additionlubricant No. 4 combines excellent cooling properties with its highlubricating value, as shown by the final lubricant temperature of 162 F.

The lubricant of the present invention also shows marked advantages overthose containing only palm oil, water, and lactic acid. In a second testwith the Falex tester, the results of which are set out in Tables IIIand IV, a series of four additional samples, Nos. 11 to 14, inclusive,were made, samples Nos. 11 and. 12 being made in a manner similar tosamples 5 and 8 above, respectively, and samples Nos. 13 and 14 beingmade in accordance with the patent to Spangler, No. 2,246,549. Thecompositions of such four samples are as follows, the acids employedbeingsolid commercial citric acid and44% commercial lactic acid in theamounts indicated.

TABLE III [Lubricant composition, per cent by weight (remainder water)]Lubricant No. Palm 011 1:3}? 212% KaPOa Each of lubricants Nos. 11 to14, inclusive, was tested in separate runs, both (A) directly aftermixing and (B) after mechanical emulsification, provided by subjectingthem to a preliminary Falex run. After each interval of .05 hourreadings were taken of the total number of notches which the adjustingmeans for the jaws of the Falex device were advanced from zero to thatpoint to maintain a constant 2500 pound load between pin and V-blocksand the temperature of the lubricant. The initial temperature of thelubricant in each test run was F. At the end of each time interval thetemperature of the lubricant in degrees Fahrenheit was recorded; suchtemperature is given in Table IV below under are very much improved overthose of the first 55 each time interval.

TABLE IV Notches Lubm Time, hours cant .05 .10 .15 .20 .25 .30 .35 .40.45 .50

11-11..." 10 15 20 21 22 22 168 170 177 181 183 185 187 100 11-13.....'0 0 s 4 15 1s 23 39 103 17s 181 187 192 199 205 205 200 900 207 20712-11"... 14 23 25 28 32 57 71 07 211 177 185 189 198 203 205 200 207206 207 12-13..." 10 14 15 21 24 25 20 188 425 Failedat 125 195 200 200207 207 207 Boiling 26min. 13-11. Failure-Blocks, Se zed to pin at 2min-19001}.

185 F. SteolPin-Sheared. l3B. Impossible. 14-1-.." fsali lulre-steel Pinsheared at 1000#. 147-18..." Impossible.

As can be seen from the test results set out in Table IV, lubricantsNos. 13 and 14, containing only palm oil, lactic acid, and water, werevery definitely inferior to lubricants Nos. 11 and 12 made in accordancewith the present invention, lubricants Nos. 13 and 14 possessing solittle lubricating properties that the terminal bearing or pin soonseized to the blocks and sheared. Tests 13-3 and 14-3 are reported asimpossible, since the mechanical emulsiflcation of mixture by a run inthe Falex tester obviously could not be accomplished. due to the failureof the terminal bearing in tests 13-A and 14A.

The reason for the remarkable improvement in lubricating properties oflubricating and cooling compounds within the scope of the presentinvention is not fully understood, but it is thought that the addition'of organic hydroxy-acids, such as citric and lactic acids, to a basiccoolant of the palm oil-potassium phosphate type produces two essentialresults:.

- water soluble inorganic salt yielding free base by 1. The provision ofa buffering agent by means of which the hydrogen ion concentration iskept constant while the soap supply is replenished.

2. The enlargement of the oil globule size to promote more effectivelubrication.

The emulsifying base, when added to the system of water and lubricatingoil of which palm oil is typical, forms soluble soaps which aredesirable in counterbalancing the formation of insoluble iron soapswhich tend to form during the cold rolling operation. Apparently,however, the emulsion so formed in prior art lubricating and coolingcompounds has a particle size which is too small to function in theoptimum manner as a lubricant. It is thought that the organichydroxy-acid coagulates the oil at many nuclei, forming fine oilglobules, which globules are however, nevertheless larger than thosewhich constituted the previous emulsion. It has been found that toproduce optimum particle sizes of such oil globules the acid should beadded only after dilution, that is, it should be the final addition tothe coolant mix. The bufiering of-the acid makes the oil lobulesavailable at optimum size, while allowing replenishment of the soapsupply.

It has been found that lubricating and cooling compounds made inaccordance with the present invention are more uniform and have lesstendency to stratify than those previously used, as typified by testlubricants Nos. 1, 2, and 3. This leads to less oil deposition on thecold strip, and consequently less dirty strip. What residue is carriedover on the strip from the mill is readily removed in alkaline cleaningsolutions, by virtue of the free soap molecules surrounding the other-.wise insoluble foreign material.

This application is a continuation-in-part of application Serial No.570,214, filed December 28,- 1944.

Whereas we have theorized concerning the reason for the improvementsresulting from the use of compositions made in accordance with ourinvention, we do not wish to be limited to such theory of operation.Having thus fully described the lubricating and cooling compounds of thepresent invention and their manner of production and use, what we desireto claim as novel is the following.

We claim:

1. A lubricating and cooling compound for cold reduction millsconsisting of the following ingredients in per cent by weight: 0.5 to10% saponifiable oil containing free fatty acid or hydrolysis andforming a soluble soap with the oil, 0.05 to 2.0% aliphatic organichydroxy-acid having a low dissociation constant and a buffering reserveof undissociated molecules. the remainder being substantially all water,said acid having been added to the compound after the oil and inorganicsalt.

3. A lubricating and cooling compound for cold reduction millsconsisting of the following ingredients in per cent by weight: 0.5 to10% oil, said oil being essentially palm oil, 0.05 to 2.0% potassiumphosphate, 0.05 to 2.0% citric acid, th remainder being substantiallyall water, said acid having been added to the compound after the oil andpotassium phosphate.

4. A lubricating and cooling compound for cold reduction millsconsisting of the following ingredients in per cent byw-eight: 0.5 to10% 011, said oil being essentially palm oil, 0.05 to 2.0%

- potassium phosphate, 0.05 to 2.0% lactic acid,

the remainder being substantially all water, said acid having been addedto the compound after the oil and potassium phosphate.

5. A lubricating and cooling compound for cold reduction millsconsisting of the following in gredients in per cent by weight: 0.5 to10% saponiflable oil containing a free fatty acid or acids, 0.05 to 2.0%Water soluble inorganic salt yielding free base by hydrolysis andforming a soluble soap with the oil, and from 0.05 to 2.0% aliphaticorganic hydroxy-acid having a low dissociation constant and a bufferingreserve of undissociated molecules, said acid having been added to thecompound after the oil and the inorganic salt, the remainder beingsubstantially all water.

6. A lubricating and cooling compound for cold reduction millsconsisting of the following ingredients in per cent by weight: 0.5 to10% oil, said oil being essentially palm oil, 0.05 to 2.0% water solublealkali metal salt of a weak inorganic acid, said salt yielding free baseby hydrolysis and forming a soluble soap with the oil, and from 0.005 to2.0% aliphatic organic hydroxy-acid having a low dissociation constantand a buffering reserve of undissociated molecules, said acid havingbeen added to the compound after the oil and the inorganic salt, theremainder being substantially all Water.

HAROLD F. MILLER. SAMUEL J. MOORE.

REFERENCES CITED The following references are of record 'in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 154,130 Eggleston Aug. 18, 1874215,875 Brown May 27, 1879 224,829 Kennerson Feb. 24, 1880 2,246,549Spengler June 24, 1941 2,252,385 Orozco Aug. 12, 1941 Zimmer Oct. 7,1941 9 Certificate of Correction 1 ?sttentNo.v 2,432,784. December 16,1947.

HAROLD 'FVMILLER ET AL. It is hereby certified that error appears in theprinted specification of theebove follows: Column 8, line 55, claim 6,for

numbered patent requiring correctlon as 7 Patent should be read withthis correction v 0.005 read 0.05; endthat the said Letters therein thatthe same may conform to the record of the case 1n the Patent Ofiice.

Signed and sealed this 30th day of March, A. D. 1948.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

